For many years, electric trolling motors have been used in conjunction with sonar depth finders, and particularly by sport fishermen, as a fishing aid. The sonar depth finders help the fisherman to find desirable fish habitat, underwater bottom features and cover such as brush piles and underwater grass. This information is extremely helpful for a fisherman to locate likely places to catch fish. The electric trolling motor is a small electric motor mounted either on the bow or stern of a fishing boat, and is used to maneuver the boat in the water, with minimal noise and disruption of the water.
The depth finders used in this manner require a transducer which transmits a sonar signal into the water and receives the returned echo, displaying the depth. In addition, the depth finder displays a signal indicative of other things between the bottom and the transducer, such as grass, brush, and occasionally fish. Often, sonar transducers have been attached to the trolling motor in order to position the transducer in the water, and allow its quick withdrawal from the water when moving the boat under power of a larger internal combustion engine. Such transducers have often been clamped to the electric motor housing, or attached to the motor mounting shaft, and connected to the sonar depth finder display head by means of a cable which would extend along the motor mounting shaft.
One problem with this arrangement, though, has been that repeated raising and lowering of the electric trolling motor on its mounting bracket would occasionally damage the transducer or the cable, rendering the sonar depth finder inoperative. Moreover, the transducer occasionally would strike an underwater object such as a stump, a rock, or the like, and damage to the transducer would result.
U.S. Pat. No. 4,737,940 provided an improved transducer mounting arrangement in which the transducer was mounted in a recess in the trolling motor housing in such a way that only the operative or discharge face of the transducer was exposed to the water, thus minimizing damage to the transducer by contacting underwater object. In addition, the cable for the transducer extended internally of the motor housing and the motor mounting shaft, thus protecting the cable itself from damage. This improvement represented a significant advance in the trolling motor and depth finder field.
However, occasionally a transducer fails from internal electrical or mechanical problems and must be replaced. In order to replace such a built in transducer, it is necessary to completely disassemble the trolling motor, remove the defective transducer and its cable, and then thread the new cable back through the trolling motor housing and shaft and re-seal the transducer in its socket in the motor housing in order to make certain that water did not enter the motor housing. This has been a very time consuming operation, which could prevent the user from fishing for several days.
The transducer itself used in the past either internally housed or externally attached to the trolling motor has been a small cylindrical puck, generally about one inch in diameter and up to an inch in height, with the actual crystal transducer being potted inside the puck. The cable is sealed as well by the potting material. Such a structure provides a high degree of protection for the transducer, but nonetheless, failures of the transducer do occur.
The present invention has as its primary object to provide a transducer for use in an electric trolling motor which overcomes the disadvantages of prior art transducers.
Another object of the invention is to provide an improved transducer which may be easily and quickly replaced without a need to disassemble the trolling motor.
Still another object of the invention is to provide an improved mounting arrangement for securely retaining a replaceable transducer in a socket in an electric trolling motor housing.
A further object of the invention is to provide a replaceable sonar transducer which may be mounted in an electric trolling motor housing while protecting the electric motor from damage by water leakage.
Yet another object of the invention is to provide a replaceable sonar transducer which is securely held in a recess in a trolling motor housing.
Still a further object of the invention is to provide an improved electric trolling motor having a replaceable sonar transducer mounted in the housing thereof in a water tight manner.